7. Project Summary/Abstract Olfactory receptors are one of the largest family of chemical cell-surface receptors in humans, and ectopically expressed olfactory receptors (exORs) have been found in 16 different tissues, including the lungs, kidneys and colon. In non-olfactory tissue, exORs do not detect ?odors?, but drive a number of biological process, including chemotaxis, development, and angiogenesis. Understanding the role of exORs in human health?including which exORs are medically relevant, and what compounds activate exORs in the endogenous tissues?is a challenging, slow and laborious process. The downstream targets of exORs are often not known and reading out exORs activation is often not possible. Recently, the Peralta-Yahya group has developed OR-based sensors in yeast to detect chemicals in the environment for biotechnology applications, such as the detection of chemical pollutants and biofuels in aqueous medium. By expressing human ORs on the yeast cell surface and linking OR ligand binding to fluorescent protein expression, this sensor technology provides a rapid readout for OR activation. In this MIRA proposal, we set forth how the OR-based sensor technology can expedite and streamline the study of the role of exORs in human health. We will focus on applying the OR-based sensor technology to the study of exORs present in skeletal muscle cells and in the colon. In skeletal muscle cells, we will identify the endogenous chemical present in muscle cells that activates the exOR mOR23 and results in decreased myofibril branching upon muscle repair, resulting in a stronger repaired muscle. Once identified, the chemical can serve as a lead compound for the synthesis of therapeutics that improve muscle healing. Further, such a therapeutic may also have implication in the treatment of neuromuscular diseases where a large number of branched myofibrils are seen. In the colon, we hypothesize that the gut microbiota communicates with the human host via exORs and that healthy and diseased colons may different OR activation fingerprints that can be used as biomarkers to diagnose biological conditions. Identification of the specific ORs activated will provide molecular targets to, in the future, elucidate their downstream effectors to further understand the role of ORs in gut disease. Additionally, identified ORs could also function as therapeutic targets; roughly 40% of pharmaceutical targets bind G-protein coupled receptors (GPCRs), of which ORs are a subset. More generally, knowing which gut metabolites interact with human receptors, such as ORs, will fill a crucial gap in understanding the microbiome-host interactions. As part of the MIRA award, we will also interphase the OR-based sensor technology with microfluidics to enable the high- throughput screening (>107 samples/day) of non-colorimetric/non-fluorescent chemicals produced by microbes. This screening throughput will allow the application of genome and evolutionary engineering strategies, which have been shown to dramatically increase the microbial production of colorimetric chemicals. Specifically, we will apply the technology to increase the microbial production of advanced pharmaceutical intermediates.